1. Field of the invention
The present invention relates to D-ketohexose 3-epimerase, and its preparation and uses.
2. Description of the prior art
As described in Enzyme Nomenclature published by Academic Press Inc., USA, 1992, epimerases act on various saccharides. Since conventional epimerases such as ribulose-phosphate 3-epimerase (EC 5.1.3.1) and UDP glucose 4-epimerase (EC 5.1.3.2), however, mainly act on saccharides coupled with phosphates or UDP, they are not usable in industrial-scale production of free neutral saccharides. There has been known only two epimerases, i.e., aldose 1-epimerase (EC 5.1.3.3) and cellobiose epimerase (EC 5.1.3.11), which act on free saccharides. The former catalyzes the epimerization between .alpha.- and .beta.-anomers of aldoses at their C-1 positions, while the latter catalyzes the epimerization between .alpha.- and .beta.-anomers of cellobiose. Although there has been a great demand for epimerases which act on free ketoses, the existence of such has not been confirmed.
It has been in a great demand to obtain a ketose epimerase which acts on free ketoses, and also to establish its preparation and uses.